CN113773211A

CN113773211A - A class of large sterically hindered ligands coordinated by N and O, nickel catalyst, and preparation method and application thereof

Info

Publication number: CN113773211A
Application number: CN202111078818.1A
Authority: CN
Inventors: 简忠保; 李康康
Original assignee: Changchun Institute of Applied Chemistry of CAS
Current assignee: Changchun Institute of Applied Chemistry of CAS
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2021-12-10

Abstract

The invention provides a large sterically hindered ligand coordinated by N and O, a nickel catalyst, a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The invention adopts a step-by-step method to synthesize the target ligand, and then synthesize a kind of neutral nickel catalyst based on the cycloheptatrienone-amine skeleton, and this kind of catalyst changes the six-membered chelating ring in the salicylaldimine ligand to five-membered Ring, under the premise that its molecular formula remains unchanged, the salicylaldehyde ligand is transformed into its isomer: cycloheptatrienone-amine ligand. This kind of catalyst can efficiently catalyze the copolymerization of ethylene and acetate-5-hexenyl ester, and the _Mw of the copolymer can reach 178,000 when the insertion rate is 1.1%. Under the same conditions, the molecular weight of this series of cycloheptatrienone-amine nickel catalysts is up to 100 times higher than that of the classic salicylaldimine nickel catalysts, and polymers can still be obtained at 130°C, showing excellent thermal stability. .

Description

N, O-coordinated large steric hindrance ligand, nickel catalyst, preparation method and application thereof

Technical Field

The invention belongs to the technical field of catalyst preparation, and particularly relates to N, O coordinated large steric hindrance ligands, a nickel catalyst, and a preparation method and application thereof.

Background

Polyolefin catalysts are central to the field of polyolefin research. The current industrialized catalysts are mainly Ziegler-Natta catalysts and metallocene catalysts, and the two types of catalysts can efficiently catalyze olefin homopolymerization. In 1995, Brookhart et al reported a class of nickel and palladium diimine catalysts useful in the preparation of high molecular weight polyethylene and polyolefins having polar functional groups attached to the backbone, which began the research on olefin polymerization catalyzed by late transition metal catalysts. Subsequently, professor Grubbs et al reported a class of salicylaldiminato nickel catalysts in 2000, which resulted in high molecular weight polyethylene with low branching degree and no need of co-catalyst in the polymerization process, besides that the catalysts can catalyze polymerization in various polar solvents. In 2001, Brookhart et al reported a class of similar ketone-amine nickel catalysts, which have high activity, do not require a co-catalyst, and have better thermal stability than salicylaldiminato nickel catalysts, which highlights the advantages of five-membered chelate rings. However, these catalysts also have some disadvantages: 1) poor thermal stability, only low molecular weight polymers at high temperatures; 2) the molecular weight distribution of the obtained polymer is wide, which limits the application range of the polymer; 3) no reports on the copolymerization of the catalyst are found. The nitrogen-oxygen coordination nickel catalyst can catalyze olefin polymerization without a cocatalyst, can select a plurality of 'green solvents', such as hexane, water and the like, and has great development potential. In recent years, a lot of researches on the nickel salicylaldimine catalyst have been conducted by many researchers in order to improve its thermal stability, activity, polymer molecular weight, tolerance to polar functional groups, and the like. Such as: 1) mecking et al introduce a high steric hindrance half-sandwich substituent to promote the axial steric hindrance of the complex, thereby protecting the central metal, obtaining polyolefin with high molecular weight, and effectively promoting the thermal stability and catalytic activity of the catalyst. 2) A series of substituents with electron absorption (supply) are introduced on amine of a ligand to regulate and control the electron cloud density of a metal at the center of a complex, and Mecking and the like find that trifluoromethyl has a good effect, so that the branching degree is reduced, the molecular weight of a polymer is improved, and the service life of a catalyst is prolonged. However, two main regulatory approaches are currently available: electronic effect, space effect, the effects that these two modes can reach are limited. In addition, the steric hindrance is not favorable for the insertion of the comonomer, so that a new regulation and control means is needed to be developed to modify the salicylaldimine catalyst.

Disclosure of Invention

The invention aims to provide N, O coordinated large steric hindrance ligands, a nickel catalyst, a preparation method and application thereof, wherein the nickel catalyst has excellent catalytic performance in ethylene homopolymerization and polar monomer copolymerization.

The invention firstly provides a large steric hindrance ligand of N, O coordination, the structural formula is shown as formula (I):

in the general formula (I), R¹A long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, OCH₃、CF₃、NO₂、

Wherein R is⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂；

R²A long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, OCH₃、CF₃Or NO₂；

R³A long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, OCH₃、CF₃Or NO₂；

R⁴Represents H,

Wherein R is⁷＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂，R⁷At the ortho, meta, or para position;

R⁵a long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, C1-C20 alkoxy, CF₃、NO₂、N(CH₃)₂；

When R is¹＝R²＝R³＝R⁴When H, R⁵Is not H.

The invention also provides a preparation method of N, O coordinated large steric hindrance ligands, which comprises the following steps:

putting bromide shown in a general formula (a), boric acid shown in a general formula (b) and anhydrous sodium carbonate into a solvent, introducing nitrogen, and then adding a catalyst for reaction to obtain a ligand (I);

preferably, the molar ratio of the bromide represented by the general formula (a), the boric acid represented by the general formula (b), and the anhydrous sodium carbonate is 1: 1.5: 9.

the invention also provides a nickel catalyst, the structural formula is shown as the general formula (II):

in the general formula (II), R¹A long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, OCH₃、CF₃、NO₂、

Wherein R is⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂；

R⁴Represents H,

R⁵a long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, C1-C20 alkoxy, CF₃、NO₂、N(CH₃)₂。

The invention also provides a preparation method of the nickel catalyst shown in the general formula (II), which comprises the following steps:

the ligand (I) and (tmeda) NiMe in the general formula₂(tmeda ═ tetramethylethylenediamine) is added into an organic solvent, and then pyridine is added for reaction to obtain a nickel catalyst shown as a general formula (II);

preferably, the ligand (I), (tmeda) NiMe₂And pyridine in a molar ratio of 1: 1.05: 20.

the invention also provides a nickel catalyst, which has a structural general formula shown in the formula (III):

in the general formula (III), R¹A long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I, Br, Cl, F, OCH₃、CF₃、NO₂、

Wherein R is⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂；

R⁴Represents H,

The invention also provides a preparation method of the nickel catalyst shown in the general formula (III), which comprises the following steps:

feeding a ligand (I) in a general formula and sodium hydride into an organic solvent, stirring for reaction, and then adding a nickel source for reaction to obtain a nickel catalyst shown in a general formula (III);

preferably, the molar ratio of the ligand (I), the sodium hydride and the nickel source is 1: 1.1: 1.1.

the invention also provides application of the nickel catalyst shown in the general formula (II) and the nickel catalyst shown in the general formula (III) in catalyzing ethylene homopolymerization and polar monomer copolymerization.

The invention has the advantages of

Compared with the prior art, the invention adopts a step-by-step method to synthesize a target ligand and then synthesizes a neutral nickel catalyst based on a tropone-amine skeleton. The catalyst changes a six-membered chelate ring in a salicylaldehyde imine ligand into a five-membered ring, and the salicylaldehyde ligand is changed into an isomer, namely a tropone-amine ligand on the premise that the molecular formula of the salicylaldehyde imine ligand is not changed. Meanwhile, the catalyst can catalyze polymerization reaction with high efficiency. The experimental results show that: the catalyst is used for ethylene homopolymerization:

1) under the condition of ethylene pressure of 8bar, the polymerization time is 30 minutes, and then the ultrahigh molecular weight polyethylene M can be obtained_wUp to 221 ten thousand;

2) when the polymerization temperature is 40 ℃ or lower, living polymerization is characteristic.

3) The catalyst can efficiently catalyze the copolymerization of ethylene and acetic acid-5-hexenyl ester, and the copolymer M is obtained when the insertion rate is 1.1 percent_wCan reach 17.8 ten thousand. Under the same conditions, compared with the classical nickel salicylaldiminate catalyst, the series of nickel tropone-amine catalysts have the advantages that the molecular weight is improved by 100 times at most, and polymers can still be obtained at 130 ℃, so that the nickel tropone-amine catalysts show excellent thermal stability.

Drawings

FIG. 1 is a single crystal diffractogram of the catalyst represented by Table 4, item 2 of example 6;

FIG. 2 is a NMR spectrum of the catalyst represented by Table 4, item 2 in example 6;

FIG. 3 is a NMR carbon spectrum of the catalyst represented by Table 4, entry 2 in example 6;

FIG. 4 is a NMR spectrum of the catalyst represented by Table 8, item 4 in example 10.

Detailed Description

(phenyl and its derivatives, R⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂(R⁶At meta-or para-),

(naphthyl and its derivatives, R⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂)、

(Anthracene radical and derivatives thereof, R⁶＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂)；

R⁴Represents H or

(R⁷＝H、CH₃、^tBu (tert-butyl), OCH₃、CF₃Or NO₂(R⁷At the ortho, meta, or para position));

When R is¹＝R²＝R³＝R⁴When H, R⁵Is not H.

adding a bromide shown as a general formula (a), boric acid shown as a general formula (b) and anhydrous sodium carbonate into a solvent, introducing nitrogen to blow the solvent for preferably 15-30 min, then adding a catalyst to react, adding dichloromethane to the solvent at preferably 90-100 ℃, more preferably 95 ℃, for preferably more than 24h, more preferably 24h, washing the mixture with water for three times, purifying the mixture by column chromatography, and drying the mixture in vacuum to obtain a ligand (I); the molar ratio of the bromide represented by the general formula (a), the boric acid represented by the general formula (b), and the anhydrous sodium carbonate is preferably 1: 1.5: 9; the solvent is a mixed solvent of toluene, ethanol and water, and the volume ratio of toluene, ethanol and water is preferably 5: 2: 1. the catalyst is preferably palladium tetratriphenylphosphine, added in an amount of 2.5% of the bromide (a).

R⁴Represents H or

R⁵a long-chain alkyl group represented by H, C1 to C20,^tBu (tert-butyl), I,Br, Cl, F, alkoxy of C1-C20, CF₃、NO₂、N(CH₃)₂。

the ligand (I) and (tmeda) NiMe in the general formula₂Feeding tmeda (tetramethylethylenediamine) into an organic solvent, wherein the organic solvent is preferably toluene, adding pyridine, and reacting at room temperature for 24 hours; filtering, collecting filtrate, vacuum concentrating the filtrate, dripping into organic solvent for settling, wherein the organic solvent is preferably n-hexane or diethyl ether, separating out red solid, filtering, collecting solid, and vacuum drying to obtain nickel catalyst represented by general formula (II); the ligand (I), (tmeda) NiMe₂And pyridine are preferably present in a molar ratio of 1: 1.05: 20.

R⁴Represents H or

feeding a ligand (I) in a general formula and sodium hydride into an organic solvent, stirring for reaction, wherein the organic solvent is tetrahydrofuran, the stirring for reaction is room temperature, the reaction time is 24 hours, filtering reaction liquid after the reaction is finished, collecting filtrate, adding a nickel source into the filtrate for reaction, the reaction temperature is room temperature, the reaction time is 24 hours, filtering, collecting filtrate, pumping the filtrate to dry, recrystallizing in toluene hexane, separating out a brown solid, filtering, collecting the solid, and drying in vacuum to obtain the nickel catalyst shown in the general formula (III); the ligand (I), sodium hydride and nickel sourceThe molar ratio is preferably 1: 1.1: 1.1, the nickel source is preferably (PPh)₃)₂NiPhCl。

The application of the nickel catalyst shown in the general formula (II) and the nickel catalyst shown in the general formula (III) in the catalysis of ethylene homopolymerization specifically comprises the following steps:

drying the reactor preferably at 90 ℃ for more than 1h, then connecting with a high-pressure gas line, adjusting the temperature of the reactor to 30-130 ℃, preferably 60 ℃, adding a solvent, preferably toluene, into the reactor under an inert atmosphere, then dissolving the nickel catalyst in the solvent to obtain a catalyst solution, preferably toluene, injecting the solvent into the reactor through an injector, stirring at a stirring speed of preferably more than 750 revolutions, introducing ethylene and maintaining the pressure at 8-40atm, preferably 8atm, after reacting for 10-30min, preferably reacting for 30min, emptying the pressure reactor, adding ethanol to quench the polymerization reaction, filtering the polymer, and drying in a vacuum oven to constant weight to obtain polyethylene. The concentration of the nickel catalyst is preferably 0.5 to 3.5. mu. mol/100 ml.

The application of the nickel catalyst shown in the general formula (II) and the nickel catalyst shown in the general formula (III) in catalyzing the copolymerization of polar monomers specifically comprises the following steps:

the reactor is dried preferably at 90 ℃ for more than 1h and then connected to a high-pressure gas line, the reactor temperature is adjusted to 60-90 ℃, preferably 65 ℃, feeding a solvent, preferably toluene, and a polar monomer, preferably 5-hexenyl acetate, into a reactor under an inert atmosphere, then dissolving the nickel catalyst in a solvent to obtain a catalyst solution, wherein the solvent is preferably toluene, injecting the catalyst solution into a reactor through an injector, stirring at 750 rpm or more, introducing ethylene and maintaining the pressure at 8-40atm, preferably 8atm, reacting for 10-60min, preferably, the reaction time is 60min, the pressure reactor is evacuated, ethanol is added to quench the polymerization reaction, the polymer is filtered and dried in a vacuum oven to constant weight to obtain polyethylene. The concentration of the nickel catalyst is preferably 0.5-10. mu. mol/25 ml.

The present invention is described in further detail below with reference to specific examples, in which the starting materials are all commercially available.

Example 1

2, 6-dibromo-4-methylaniline (2.8g, 7.1mmol), 2-chloro-2, 4, 6-cycloheptatrien-1-one (1.0g, 7.1mmol), cesium carbonate (3.2g, 10.0mmol), and 1,1 '-binaphthyl-2, 2' -bis-diphenylphosphine (44.2mg, 7.1. mu. mol), tris (dibenzylideneacetone) dipalladium (36.8mg, 3.55. mu. mol) were dissolved in toluene (50mL) under an inert atmosphere (nitrogen), and then stirred at 90 ℃ for 24 hours or more. After completion of the reaction, methylene chloride (50mL) was poured into the dark red liquid mixture, and insoluble materials were filtered off. The organic layer was washed with water, separated and dried over anhydrous sodium sulfate. After filtration of the solid, the organic phase is concentrated by rotary evaporation in vacuo. The resulting residue was purified by flash column chromatography (silica gel; petroleum ether/ethyl acetate 3: 1) to yield 1.8g (70% yield) of product a as a brown powder.

¹H NMR(500MHz,298K,CDCl₃，2.50ppm)：δ8.41(s,1H),7.50(s,2H),7.36–7.32(m,2H),7.10(t,J＝10.2Hz,1H),6.83–6.77(m,1H),6.26(d,J＝10.2Hz,1H),2.38(s,3H)。

Example 2

Phenylboronic acid (0.40g, 3.3mmol), A (0.8g, 2.2mmol), sodium carbonate (2.1g, 19.8mmol), tetrakis (triphenylphosphine) palladium (58mg, 5.5. mu. mol) were dissolved in a toluene/ethanol/water mixed solution (60mL:24mL:12mL), followed by stirring at 95 ℃ for 24 hours. After completion of the reaction, methylene chloride (50mL) was poured into the dark red liquid mixture, and insoluble materials were filtered off. The organic layer was washed with water, separated and dried over anhydrous sodium sulfate. After filtration of the solid, the organic phase is concentrated by rotary evaporation in vacuo. The resulting residue was purified by flash column chromatography (silica gel; petroleum ether/ethyl acetate 2: 1) to yield 0.7g (90% yield) of product B as a yellow powder.

¹H NMR(500MHz,298K,CDCl₃，2.50ppm)：δ8.35(s,1H),7.33–7.28(m,4H),7.28(s,2H),7.26–7.22(m,4H),7.21–7.16(m,2H),7.12–7.05(m,1H),6.99(d,J＝11.6Hz,1H),6.81(d,J＝10.1Hz,1H),6.50(t,J＝9.4Hz,1H),6.33(d,J＝10.3Hz,1H),2.48(s,3H)。

Example 3

4- (Diphenylamine) phenylboronic acid (0.95g, 3.3mmol), A (0.8g, 2.2mmol), sodium carbonate (2.1g, 19.8mmol), tetrakis (triphenylphosphine) palladium (58mg, 5.5. mu. mol) were dissolved in a toluene/ethanol/water mixed solution (60mL:24mL:12mL), followed by stirring at 95 ℃ for 24 hours. After completion of the reaction, methylene chloride (50mL) was poured into the dark red liquid mixture, and insoluble materials were filtered off. The organic layer was washed with water, separated and dried over anhydrous sodium sulfate. After filtration of the solid, the organic phase is concentrated by rotary evaporation in vacuo. The resulting residue was purified by flash column chromatography (silica gel; petroleum ether/ethyl acetate 2: 1) to yield 1.37g (89% yield) of product C as a pale yellow powder.

1H NMR(500MHz,298K,CDCl3):δ8.40(s,1H),7.27(s,2H),7.20(t,J＝7.8Hz,10H),7.16(d,J＝8.6Hz,4H),7.08(d,J＝11.6Hz,1H),6.97(d,J＝8.6Hz,10H),6.93(d,J＝8.5Hz,4H),6.87(t,J＝10.1Hz,1H),6.77(d,J＝8.8Hz,1H),6.62(t,J＝9.4Hz,1H),6.36(d,J＝10.3Hz,1H),2.46(s,3H).

Table 1 shows the ligand of partial formula (I) and the yield obtained by varying the reactants (a) and (b), the specific reaction steps and conditions were the same as in example 3, the reaction temperature was 95 ℃ and the reaction time was 24 hours.

TABLE 1

Example 4

Mixing B (200mg, 0.55mmol) and (tmeda) NiMe₂(118.0mg, 0.58mmol) was dissolved in 20ml of toluene, followed by addition of pyridine (870.1mg, 11.0mmol), reaction stirred at room temperature for 24 hours, collection of the filtrate by filtration, vacuum concentration of the filtrate, dropwise addition to n-hexane for precipitation of an orange solid, filtration, collection of the solid and vacuum drying to give 254.6mg (90.0% yield) of pure catalyst D.

¹H NMR(500MHz,298K,C₆D₆):δ8.39(d,J＝5.0Hz,2H),8.08(d,J＝8.2Hz,4H),7.31(t,J＝7.7Hz,4H),7.28(s,2H),7.11–7.15(m,2H),6.80(d,J＝10.6Hz,1H),6.61(d,J＝11.5Hz,1H),6.53–6.41(m,3H),6.13(d,J＝7.4Hz,2H),6.01(t,J＝9.4Hz,1H),2.22(s,3H),-0.40(s,3H).

¹³C{¹H}NMR(126MHz,298K,C₆D₆):δ180.30(O＝C-Ar),169.28,152.01,142.48,141.59,138.24,135.30,134.91,134.74,132.89,131.66,129.88,127.16,123.24,120.92,120.36,120.22,21.04(PhCH₃),-6.54(Ni-CH₃).

A nickel catalyst of formula (II) was prepared according to the procedure and conditions of example 4, except that the ligands were varied, and the results are shown in Table 2:

table 2: synthesis example of a portion of the Nickel catalyst of the formula (II) (reaction temperature: 25 ℃ C., reaction time: 24 hours)

Example 5

C (384mg, 0.55mmol) and NaH (14.5mg, 0.61mmol) were added to 20ml of tetrahydrofuran, the reaction was stirred at room temperature for 24 hours, the filtrate was collected by filtration, and then (PPh) was added to the filtrate₃)₂NiPhCl (424.6mg, 0.61mmol), stirred at room temperature for 24h, collected by filtration, drained from the filtrate, recrystallized from toluene hexanes to give a brown solid, filtered, collected and dried in vacuo to afford 481.8mg (80.0% yield) of pure catalyst E.

¹H NMR(500MHz,298K,C₆D₆):δ7.85(d,J＝8.6Hz,4H),7.59–7.53(m,6H),7.18(d,J＝1.1Hz,3H),7.15–7.06(m,15H),7.03–6.97(m,5H),6.95–6.85(m,13H),6.77(t,J＝7.3Hz,1H),6.68(d,J＝11.5Hz,1H),6.55(d,J＝4.7Hz,2H),6.49(t,J＝7.2Hz,1H),6.42(dd,J＝9.1,11.4Hz,1H),6.34(t,J＝7.4Hz,2H),6.12–6.07(m,1H),2.11(s,3H).

¹³C{¹H}NMR(126MHz,298K,C₆D₆):δ178.94,168.18,147.51,145.70,141.29,137.40,135.56,134.98,133.45,133.37,133.27,132.38,131.01,130.66,130.19,129.22,128.69,128.38,21.86(PhCH₃).

A nickel catalyst of the formula ((III) was prepared according to the procedure and conditions of example 5, except that the ligands were varied, and the results are shown in Table 3:

table 3: synthesis example of a Nickel catalyst having partial formula (III) (reaction temperature: 25 ℃ C., reaction time: 24 hours)

EXAMPLE 6 use of Nickel catalyst

A350 mL glass pressure reactor connected to a high pressure gas line was first dried under vacuum at 90 ℃ for at least 1 h. Then, the reactor was adjusted to 50 ℃, 98mL of toluene was added to the reactor under an inert atmosphere, and then 3.5. mu. mol of the Ni catalyst represented by the formula (III) was dissolved in 2mL of toluene and injected into the polymerization system by a syringe. Under rapid stirring (750 revolutions), ethylene was passed in and maintained at 8 bar. After 30min, the pressure reactor was evacuated, 200mL of ethanol was added to quench the polymerization, the polymer was filtered, and dried in a vacuum oven to constant weight. The effect of different nickel catalysts on ethylene polymerization is shown in table 4.

TABLE 4 different Nickel catalysts (varying substituent R)¹、R⁵、R⁶) Influence on ethylene polymerization

Reaction conditions are as follows: nickel phenyl triphenylphosphine catalyst (3.5. mu. mol), toluene (100mL), ethylene pressure (8bar), polymerization time (30min), polymerization temperature (50 ℃ C.), all data are based on at least the results of two parallel experiments (unless otherwise stated). Activity: at 10⁵g mol^-1h^-1Is a unit. M_w、M_w/M_n: weight average molecular weight, polymer dispersibility index, respectively, at 150 ℃ in 1,2, 4-trichlorobenzene, relative to polystyrene standards, determined by GPC. The degree of branching is the number of branches per 1000 carbons and is determined by nuclear magnetic resonance hydrogen spectroscopy. The single crystal diffractogram, nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum of the catalyst represented by item 2 in Table 4 in example 6 are shown in FIGS. 1 to 3.

Note: items 1 to 18: nickel catalyst (R)²＝H，R³＝H，R⁴H); items 13 to 14: nickel catalyst

Items 15 to 16: nickel catalyst

Items 17 to 18: nickel catalyst

The data in table 4 illustrates: when the catalyst substituent R is controlled¹、R²、R³、R⁴Without changing, by changing the substituents R⁵Under the same polymerization conditions (time, temperature, pressure are the same), the volume of the radical increases (CH)₃、OCH₃、N(CH₃)₂t-Bu), the activity decreases, both the molecular weight and the activity increase; when the substituent is an electron-withdrawing substituent, both the polymerization activity and the molecular weight are reduced, and the branching degree is lower. When the catalyst substituent R is controlled²、R³、R⁴、R⁵Invariant, variant substituents R¹When the polymerization is carried out, the polymerization molecular weight and the activity are rapidly increased along with the increase of steric hindrance, because the central metal is protected by the large steric hindrance group in the catalyst, and the reduction of the polymer molecular weight caused by the elimination of beta-H is not easy to generate.

EXAMPLE 7 use of Nickel catalyst

A350 mL glass pressure reactor connected to a high pressure gas line was first dried under vacuum at 90 ℃ for at least 1 h. Then, the reactor was adjusted to 50 ℃, 98mL of toluene was added to the reactor under an inert atmosphere, and then 3.5. mu. mol of the Ni catalyst represented by the formula (II) was dissolved in 2mL of toluene and injected into the polymerization system by a syringe. Under rapid stirring (750 revolutions), ethylene was passed in and maintained at 8 bar. After 30min, the pressure reactor was evacuated, 200mL of ethanol was added to quench the polymerization, the polymer was filtered, and dried in a vacuum oven to constant weight. The effect of different reaction conditions on the nickel catalyst catalyzed ethylene polymerization is shown in table 5.

TABLE 5 different Nickel catalysts (varying substituent R)²、R³、R⁴、R⁷) Influence on ethylene polymerization

Reaction conditions are as follows: nickel picoline catalyst (3.5. mu. mol), toluene (100mL), ethylene pressure (8bar), polymerization time (3. mu. mol)0min), polymerization temperature (50 ℃), all data being based at least on the results obtained in two parallel tests (unless otherwise stated). Activity: at 10⁵g mol^-1h^-1Is a unit. M_w、M_w/M_n: weight average molecular weight, polymer dispersibility index, respectively, at 150 ℃ in 1,2, 4-trichlorobenzene, relative to polystyrene standards, determined by GPC. The degree of branching is the number of branches per 1000 carbons and is determined by nuclear magnetic resonance hydrogen spectroscopy.

Note: items 1 to 17: nickel catalyst (R)¹＝H，R⁵＝CH₃) (ii) a Entries 2 to 4: nickel catalyst

Entries 5 to 7: nickel catalyst

Entries 8 to 10: nickel catalyst

Table 5 the data illustrates: when the catalyst substituent R is controlled¹、R²、R³、R⁵Without changing, by changing the substituents R⁴In the case of the same polymerization conditions (time, temperature, pressure are the same), depending on R⁴Increase in radical volume (H, Ph, Biphenyl, Ph)₂N), the activity is reduced, the molecular weight is increased and then reduced, because the central metal is protected by the large steric hindrance group in the catalyst, the elimination of beta-H is not easy to generate, but when the steric hindrance is too large, the speed of inserting ethylene is influenced, the chain growth is slowed down in the same time, and the molecular weight of the polymer is reduced on the contrary. In addition, the large steric hindrance hinders the insertion of ethylene, and the polymerization activity is in turn decreased. When the catalyst substituent R is controlled¹、R²、R⁴、R⁵Without changing, by changing the substituents R³In the case of the same polymerization conditions (time, temperature, pressure are the same), R³If it is a strongly electron-withdrawing group (CF)₃、NO₂) The molecular weight can be significantly increased and the branching degree can be reduced, but the activity is reduced. When controlling the catalystSubstituent R¹、R³、R⁴、R⁵When not changed, R²When the catalyst is an electron-withdrawing group, the activity of the catalyst is reduced, the activity is increased, and the branching degree is reduced.

EXAMPLE 8 use of Nickel catalyst

First, a 350mL glass pressure reactor or a 200mL steel kettle reactor, connected to a high pressure gas line, was dried under vacuum at 90 ℃ for at least 1 h. Then the reactor was adjusted to a desired temperature, 98mL of a solvent was added to the reactor under an inert atmosphere, and then a specific amount of the Ni catalyst represented by the formula (II) was dissolved in 2mL of the same solvent and injected into the polymerization system by a syringe. Under rapid stirring (750 revolutions), ethylene was passed in and maintained at the desired pressure. After a certain time, the pressure reactor was evacuated, 200mL of ethanol was added to quench the polymerization, the polymer was filtered and dried in a vacuum oven to constant weight. The effect of different reaction conditions on the nickel catalyst catalyzed ethylene polymerization is shown in table 6.

TABLE 6 influence of reaction conditions on the catalysis of ethylene polymerization by nickel troponinamine catalysts

Wherein, nickel picoline catalyst: (

R²＝H,R³＝CF₃,R⁴＝H,R⁵＝CH₃) All data are based on the results of at least two parallel experiments (unless otherwise indicated). Pressure: taking bar as a unit; time: taking min as a unit; temperature: in units of ℃ C; yield: taking g as a unit; activity of 10⁵g mol^-1h^-1Is a unit; m_wAt 10⁵g mol^-1Is a unit. M_w、M_w/M_n: weight average molecular weight, polymer dispersibility index, respectively, at 150 ℃ in 1,2, 4-trichlorobenzene, relative to polystyrene standards, determined by GPC. The degree of branching is the number of branches per 1000 carbons and is determined by nuclear magnetic resonance hydrogen spectroscopy.

Note: items 1 to 8: the dosage of the nickel catalyst is 3.5 mu mol; item 9: the dosage of the nickel catalyst is 1 mu mol; items 10 to 12: the dosage of the nickel catalyst is 0.5 mu mol; items 13 to 16: the amount of nickel catalyst used was 2. mu. mol.

Table 6 the data illustrates: controlling the nickel catalyst constant (

R²＝CF₃,R³H), ethylene pressure 8bar, polymerization time 30min, polymerization temperature from 30 ℃ to 130 ℃, molecular weight and activity increase first and then decrease, branching degree gradually increases. The highest molecular weight (M) at 50 ℃_w221.1 ten thousand) with the highest activity at 60 ℃. When the ethylene pressure is 40bar, the polymerization time is 30min, the polymerization temperature is changed from 30 ℃ to 50 ℃, the molecular weight and the activity are gradually increased, the branching degree is not greatly changed, and the molecular weight reaches the maximum (M) at 50 ℃_w354.7 ten thousand). When THF is used as a polymerization solvent, the molecular weight of the resulting polymer decreases, the polymerization activity decreases, and the degree of branching does not change much. Polymerization in toluene was carried out while keeping the ethylene pressure constant (8bar), and the polymerization activity and the molecular weight of the polymer gradually increased with the lapse of time, which was characterized by living polymerization.

EXAMPLE 9 use of Nickel catalyst

A75 mL glass pressure reactor connected to a high pressure gas line was first dried under vacuum at 90 ℃ for at least 1 h. Then, the reactor was adjusted to 70 ℃, 23mL of toluene and 0.27mL of 5-hexenyl acetate were added to the reactor under an inert atmosphere, and then 10.0. mu. mol of the Ni catalyst represented by formula (II) was dissolved in 2mL of toluene and injected into the polymerization system by a syringe. Under rapid stirring (750 revolutions), ethylene was passed in and maintained at 8 bar. After 60min, the pressure reactor was evacuated, 200mL of ethanol was added to quench the polymerization, the polymer was filtered, and dried in a vacuum oven to constant weight. The effect of the nickel catalyst on the ethylene polymerization under different reaction conditions is shown in table 7.

TABLE 7 different Nickel catalysts (varying substituent R)¹、R³、R⁴) Effect on copolymerization of ethylene and polar monomers

Reaction conditions are as follows: nickel picoline catalyst (10.0. mu. mol), toluene (25mL), ethylene pressure (8bar), 5-hexenyl acetate (0.1M) polymerization time (60min), polymerization temperature (70 ℃), all data being based on at least the results of two parallel experiments (unless otherwise stated). Activity: at 10⁵g mol^-1h^-1Is a unit. M_w、M_w/M_n: weight average molecular weight, polymer dispersibility index, respectively, at 150 ℃ in 1,2, 4-trichlorobenzene, relative to polystyrene standards, determined by GPC. The degree of branching is the number of branches per 1000 carbons and is determined by nuclear magnetic resonance hydrogen spectroscopy.

Note: items 1 to 9: nickel catalyst (R)²＝H,R⁵＝CH₃)。

Table 7 data illustrates: when the catalyst substituent R is controlled¹、R²Without changing, by changing the substituents R³In the case of the same polymerization conditions (time, temperature, pressure are the same), depending on R³Increase in radical volume (H, Ph, Biphenyl, Ph)₂N), overall reduced activity, reduced molecular weight, due to the large steric hindrance groups in the catalyst, which affects the rate of insertion of polar monomers, resulting in slower chain growth and reduced polymer molecular weight at the same time. R¹、R³Invariable, R²Is an electron withdrawing group (CF)₃、NO₂) The polymer has higher molecular weight, increased activity, reduced branching degree and reduced insertion rate of polar monomer. When the catalyst substituent R is controlled²、R³Without changing, by changing the substituents R¹In the case of the same polymerization conditions (time, temperature, pressure are the same), R¹If it is a large steric hindrance group (Anthryl), it has higher molecular weight and is higher than that of the large steric hindrance group (Anthryl)The low branching degree and the existence of ortho-position large steric hindrance substituent enhance the stability of the catalyst, so that the molecular weight of the polymer is increased, and the branching degree is reduced.

EXAMPLE 10 use of Nickel catalyst

A75 mL glass pressure reactor connected to a high pressure gas line was first dried under vacuum at 90 ℃ for at least 1 h. Then, the reactor was adjusted to a desired temperature, 23mL of toluene and a specific amount of 5-hexenyl acetate were added to the reactor under an inert atmosphere, and then 10.0. mu. mol of the Ni catalyst represented by formula (II) was dissolved in 2mL of toluene and injected into the polymerization system by a syringe. Under rapid stirring (750 revolutions), ethylene was passed in and maintained at the desired pressure. After a specified time, the pressure reactor was evacuated, the polymerization was quenched by the addition of 200mL of ethanol, the polymer was filtered, and dried in a vacuum oven to constant weight.

TABLE 8 influence of reaction conditions on the copolymerization of ethylene polar monomers catalyzed by nickel tropone amine catalysts

Reaction conditions are as follows: nickel methylpyridine catalyst (

R²＝R⁴＝H,R³＝CF₃,R⁵＝CH₃) Nickel catalyst (10.0. mu. mol), toluene (25mL), ethylene pressure (8bar), monomer (5-hexenyl acetate), polymerization time (60 min). All data are based on results from at least two parallel experiments (unless otherwise indicated). Temperature: in units of ℃ C; activity of 10⁵g mol^-1h^-1Is a unit. M_w、M_w/M_n: weight average molecular weight, polymer dispersibility index, respectively, at 150 ℃ in 1,2, 4-trichlorobenzene, relative to polystyrene standards, determined by GPC. The degree of branching is the number of branches per 1000 carbons and is determined by nuclear magnetic resonance hydrogen spectroscopy. The nmr hydrogen spectrum of the catalyst represented by entry 4 of table 8 is shown in fig. 4.

Note: item 2: the polymerization time is 25min, and the others are 60 min; item 7: the ethylene pressure was 4bar, the others 8 bar.

The data in table 8 illustrates: controlling the nickel catalyst constant (

R²＝R⁴＝H,R³＝CF₃,R⁵＝CH₃) When the ethylene pressure is 8bar and the polymerization temperature is 60-65 ℃, the molecular weight and the activity of the copolymer are reduced, the insertion rate is increased, and the high temperature is favorable for the insertion of polar monomers. The polymerization temperature is controlled to be 65 ℃, the pressure is 8bar, the molecular weight and the activity of the copolymer are gradually reduced along with the gradual increase of the concentration of the polar monomer, and the insertion rate is gradually increased. When the ethylene pressure is changed to 4bar, the molecular weight of the obtained polymer is reduced, the polymerization activity is reduced, and the insertion rate of the polar monomer is increased.

Claims

1. the large sterically hindered ligand of a class of N, O coordination, is characterized in that, structural formula is shown in formula (I):

In the general formula (I), R ¹ represents H, a C1-C20 long-chain alkyl group, ^t Bu, I, Br, Cl, F, OCH ₃ , CF ₃ , NO ₂ ,

wherein R ⁶ =H, CH ₃ , ^tBu , OCH ₃ , CF ₃ or NO ₂ ;

R ² represents H, C1-C20 long-chain alkyl, ^t Bu, I, Br, Cl, F, OCH ₃ , CF ₃ or NO ₂ ;

R ³ represents H, C1-C20 long-chain alkyl, ^t Bu, I, Br, Cl, F, OCH ₃ , CF ₃ or NO ₂ ;

R ⁴ represents H,

wherein R ⁷ =H, CH ₃ , ^tBu , OCH ₃ , CF ₃ or NO ₂ , and R ⁷ is in the ortho position, meta position, or para position;

R ⁵ represents H, C1-C20 long-chain alkyl, ^tBu , I, Br, Cl, F, C1-C20 alkoxy, CF ₃ , NO ₂ , N(CH ₃ ) ₂ ;

When R ¹ =R ² =R ³ =R ⁴ =H, R ⁵ is not H.

2. the preparation method of the large sterically hindered ligand of a class of N, O coordination according to claim 1, is characterized in that, comprises:

Bromide shown in general formula (a), boric acid shown in general formula (b), anhydrous sodium carbonate are thrown into the solvent, feed nitrogen, then add catalyst reaction to obtain ligand (I);

3. the preparation method of the large sterically hindered ligand of a class of N, O coordination according to claim 2, is characterized in that, described bromide shown in general formula (a), shown in general formula (b) The molar ratio of boric acid and anhydrous sodium carbonate is 1:1.5:9.

4. a nickel catalyst is characterized in that, structural formula is shown in general formula (II):

In the general formula (II), R ¹ represents H, a C1-C20 long-chain alkyl group, ^t Bu, I, Br, Cl, F, OCH ₃ , CF ₃ , NO ₂ ,

wherein R ⁶ =H, CH ₃ , ^tBu , OCH ₃ , CF ₃ or NO ₂ ;

R ⁴ represents H,

R ⁵ represents H, a C1-C20 long-chain alkyl group, ^tBu , I, Br, Cl, F, a C1-C20 alkoxy group, CF ₃ , NO ₂ , and N(CH ₃ ) ₂ .

5. the preparation method of nickel catalyst shown in a kind of general formula (II) described in claim 4, is characterized in that, comprises:

The general formula ligand (I), (tmeda) NiMe ₂ (tmeda=tetramethylethylenediamine) are fed into the organic solvent, and then pyridine is added to react to obtain the nickel catalyst shown in the general formula (II);

6. the preparation method of nickel catalyst shown in a kind of general formula (II) according to claim 5 is characterized in that, the mol ratio of described part (I), (tmeda) NiMe ₂ and pyridine is 1: 1.05:20.

7. a nickel catalyst, is characterized in that, general structural formula is shown in formula (III):

In the general formula (III), R ¹ represents H, a C1-C20 long-chain alkyl group, ^t Bu, I, Br, Cl, F, OCH ₃ , CF ₃ , NO ₂ ,

wherein R ⁶ =H, CH ₃ , ^tBu , OCH ₃ , CF ₃ or NO ₂ ;

R ⁴ represents H,

8. the preparation method of nickel catalyst shown in a kind of general formula (III) described in claim 7, is characterized in that, comprises:

The general formula ligand (I) and sodium hydride are fed into the organic solvent for stirring reaction, and then a nickel source is added to react to obtain the nickel catalyst shown in the general formula (III);

9. the preparation method of the nickel catalyst shown in a kind of general formula (III) according to claim 8, is characterized in that, the mol ratio of described ligand (I), sodium hydride and nickel source is 1:1.1:1.1 .

10. The application of the nickel catalyst represented by the general formula (II) of claim 4 or the nickel catalyst represented by the general formula (III) of claim 7 in catalyzing the homopolymerization of ethylene and the copolymerization of polar monomers.